What are the parts of a metal block plane?

13th August 2021


	What are the parts of a metal block plane?


	Shop for Woodworking Hand Planes




			Although they all look fairly similar, metal block planes vary in the design of their adjustment mechanisms and lever caps, and the shape of their lateral iron adjusters.

			Some block planes have Norris-style adjusters that adjust the lateral angle of the iron (its horizontal alignment with the sole across the mouth of the plane) as well as its depth. See What is a Norris-style adjuster? for more information about the advantages and disadvantages of this type of adjuster.

			Others have vertically-mounted iron depth adjusters and a separate lateral adjuster.

			And there are block planes with adjusters that are fitted at the same angle as Norris adjusters, but adjust only the depth of the iron, and lateral adjusters that look like metal frames with wings.

			Wonkee’s guide to block plane parts is based on one particular style of block plane, but points out many of the differences in design along the way.



			Body
			The body, or the base of the plane, to which all other parts are attached, is usually made of cast iron, but more expensive ones are made of brass or bronze. Bronze is an alloy (a mixture) of copper and tin, and brass is an alloy of copper and zinc.

			Some parts of the body – notably the sole and the bed, the area where the blade is seated – are “machined”: that is, they are milled or ground on machines to make them perfectly flat, which is vital if the plane is to cut accurately.

			Iron
			The iron can be bedded at at 12 degrees (low angle block plane) or 20 degrees (standard block plane), and sits bevel up in metal versions of the plane. Because the bevel is on the front of the iron and therefore meets the wood it is cutting, its angle is added to the bedding angle, or pitch, to give the overall cutting angle.

			For instance, an iron with a pitch of 12 degrees and a bevel of 25 degrees has an effective cutting angle of 37 degrees.

			The iron of a metal block plane often has a series of lateral slots cut into it. These are for the lug or “tooth” of the iron adjustment mechanism to fit into. As the iron is repeatedly sharpened, it will get shorter, and so the lug will go into a higher slot, and so on until eventually all the slots have been used, and it’s time to buy a new iron.

			Lever cap
			The lever cap holds the iron in place and can follow one of several designs, including cam lever and knuckle joint fasteners.

			Cam lever and lever cap screw On some metal block planes, there is a cam lever which, when turned to the locked position, levers the cap against the lever cap screw that goes through the cap and into the body of the plane. This levering action holds the iron firmly in place.

			Knuckle joint Lever caps on some other block planes have a knuckle joint mechanism. The keyhole slot of the cap goes under the lever cap screw and the hinged top of the lever cap – which is rounded rather like the back of a deep spoon – is pressed down until it snaps into the locked position to secure the blade.

			Thumbwheel And there’s yet another lever cap design. This one has a large thumbwheel which is turned to tighten the cap, putting pressure on the iron to hold it in place. The thumbwheel can be under the hood of the lever cap . . .

			. . . or over the top of the cap.

			Block planes with this type of lever cap thumbwheel usually don’t have a screw to hold the cap in place; instead, they have a crossbar.

			Iron depth adjuster
			Types of iron depth adjuster used in block planes include a vertically-mounted one, and one that sticks out from the back of the plane. The wheels on the adjusters are often knurled – that is, a diamond-shaped (criss-cross) pattern is cut into the metal to give extra grip for the fingers.

			A third type is the Norris-style adjuster, which adjusts the iron for depth and lateral position, so a plane with this type of adjuster does not need a separate lateral adjuster. Some cheaper block planes have no iron adjustment mechanism – the blade is simply adjusted by hand after loosening the lever cap.

			Lateral adjustment lever
			The lateral adjustment lever, where fitted, sits beneath the iron and has a bar that extends outwards and then downwards from the rear of the plane. Moving it left or right adjusts the blade’s lateral angle – which should be parallel to the sole across the width of the plane.A small circular plate on the adjustment lever fits into a slot in the iron. When the pivoted lever is moved, the blade is levered left or right.

			Sole
			The soles of most block planes are split into two parts – a front plate, which is adjustable backwards and forwards to set the mouth opening, and the main part from the mouth to the heel of the plane.

			Mouth
			The mouth is adjusted to allow different thicknesses of shaving (the chip) to pass up through the throat of the plane (the area above the mouth). A tight mouth is called for when the iron’s depth is set to take a very thin shaving, and a wide mouth when it’s set to take thicker shavings.

			Mouth adjustment lever
			The mouth is usually adjusted by means of an adjustment lever which is located below the front knob. The knob is turned anti-clockwise to release the lever, which is then turned to adjust the mouth setting. Turning the front knob clockwise locks the lever, keeping the mouth at the new setting.

			On some block planes, there is no adjustment lever – the plate is moved backwards and forwards by pressure on the knob after it has been loosened. And some metal block planes don’t have adjustable mouths at all.

			Front knob
			The front knob, usually made of steel or brass, has a rounded recess in its top. Block planes are held in the palm of the hand while the tip of the user’s index finger rests in the indentation on the top of the knob, which helps with the guiding of the plane.

			Dimple
			With the “hood” or rounded portion of the lever cap in the palm of the hand and the forefinger in the recess of the knob, the natural position for the other fingers and the thumb is the cheeks of the plane, which are dimpled for this very purpose.

			If two-handed planing is called for (perhaps on hard wood when lots of pressure is needed), the thumb of the non-dominant hand can be placed in the knob recess.